Boris Johnson today announced plans to retrain Londoners left unemployed by the economic downturn as energy efficiency advisers in a drive to make the capital greener.

The mayor of London unveiled proposals to set up a "retrofitting academy" to train an army of energy advisers as he aired his ambitions to place the city at the forefront of green industry.

The move would prove vital to Britain and London as unemployment rises in the recession, he told a City Hall gathering for members of the Green500 and Better Buildings Partnership.

The schemes provide support for large companies committed to cutting carbon emissions in line with the mayor's target of a 60% reduction by 2025 from 1990 levels, which promises to shave at least 20% off their energy bills.

Johnson told delegates he was interested in introducing an insulation scheme similar to one established in Kirklees, Yorkshire, where every resident is advised on how to reduce energy bills with better insulation and energy saving measures, such as combined heat and power boilers, and retrofitting is provided for free.

The Conservative mayor said: "That's why we are proceeding with a retrofitting academy, which I think would be a huge benefit to this city at a time when we expect people to be joining the ranks of unemployment. They will need retraining and they will be retrained in an industry which has a huge potential for growth."

Johnson also vowed to push ahead with the retrofitting of buildings in London that in one way or another reside in the public sector – believed to be around 25% of all buildings in the capital.

And he said he would use his "considerable" powers in public procurement to drive forward "the electrification or the low carbonificaton" of City Hall's motor fleet to help London become the capital of green industry.

Johnson said his ambition to boost low-carbon technology could "help replace in the economy of London the activity that quite frankly we may lose in the next 18 months or so in the City of London".

Darren Johnson, a Green member of the London assembly, welcomed plans to boost the number of skilled retrofitters in the capital, but criticised the mayor's decision to drop a one-stop-shop service for Londoners wanting advice on insulation and energy conservation, which was part of the Green Homes Initiative.

Residents seeking advice on saving energy were in effect left in limbo until the mayor introduces the Kirklees-style insulation scheme, said Darren Johnson.

He added: "Insulation in the public and commercial sector is welcome but they have dropped the third stand, which is for domestic consumers. We are not going to get properly insulated if we ignore the domestic consumer."

The Green Homes programme was first set up under the previous mayor, Ken Livingstone, around the same time that the Green500 was established.

Despite its name, the Green500 has 154 large businesses and public sector members, of which just 17 have so far signed up to detailed carbon-reduction action plans.

It has a target to cut London's yearly CO2 emissions by 1.5m tonnes, saving at least £2.5m in energy bills.

The mayor said: "Creating a low-carbon, clean and more pleasant city that exploits new 'green' technologies is a key part of my vision to help London through the downturn. An attractive, less polluted city is a place where people will want to live, work and visit. Top-name London companies from all sectors are here today to demonstrate their commitment to cutting the capital's carbon emissions. I urge others to do the same."